Lightest Higgs Boson Mass Research Articles

Nonholomorphic soft-term contributions to the Higgs-boson masses in the Feynman diagrammatic approach

We study the effects of non-holomprphic soft SUSY-breaking terms added to the Minimal Supersymmetric Standard Model (MSSM) on the Higgs-boson masses. The calculation of the non-holomorphic contributions is perfromed at the one-loop level in the Feynman diagramatic approach. After generating a FeynArts model file with the help of SARAH, we calculate the renormalized Higgs-boson self-energies at the one-loop level using the FeynArts/FormCalc setup. The results obtained from FeynArts/FormCalc are fed to FeynHiggs to estimate the contributions to the neutral CP-even Higgs-boson masses, $M_{h,H}$, as well as to the charged Higgs-boson mass, $M_{H^{\pm}}$. For the specific set of parameter points that we choose for this study, the non-holomorphic soft-term contributions to the CP-even light Higgs boson mass $M_h$, contrary to claims in the literature, turn out to be very small. For the CP-even heavy Higgs boson mass, $M_{H}$, as well as for the charged Higgs boson mass, $M_{H^{\pm}}$, the contributions can be substantially larger for some parts of parameter space.

The Higgs boson mass as fundamental parameter of the minimal supersymmetric standard model

In the Minimal Supersymmetric Standard Model (MSSM) the mass of the lightest neutral Higgs boson is determined by the supersymmetric parameters. In the m_hMSSM the precisely measured Higgs boson replaces the trilinear coupling A_t as input parameter. Expressions are derived to extract A_t in a semi-analytical form as a function of the light Higgs boson (pole) mass. An algorithm is developed and implemented at two-loop precision, generalizable to higher orders, to perform this inversion consistently. The result of the algorithm, implemented in the SuSpect spectrum calculator, is illustrated on a parameter set compatible with LHC measurements.

Supersymmetric particle and Higgs boson masses from the landscape: Dynamical versus spontaneous supersymmetry breaking

Perturbative supersymmetry breaking on the landscape of string vacua is expected to favor large soft terms as a power-law or log distribution, but tempered by an anthropic veto of inappropriate vacua or vacua leading to too large a value for the derived weak scale -- a violation of the atomic principle. Indeed, scans of such vacua yield a statistical prediction for light Higgs boson mass m_h~ 125 GeV with sparticles (save possibly light higgsinos) typically beyond LHC reach. In contrast, models of dynamical SUSY breaking (DSB) -- with a hidden sector gauge coupling g^2 scanned uniformly -- lead to gaugino condensation and a uniform distribution of soft parameters on a log scale. Then soft terms are expected to be distributed as $m_{\rm soft}^{-1}$ favoring small values. A scan of DSB soft terms generally leads to $m_h\ll 125$ GeV and sparticle masses usually below LHC limits. Thus, the DSB landscape scenario seems excluded from LHC search results. An alternative is that the exponential suppression of the weak scale is set anthropically on the landscape via the atomic principle.

Spinning no-scale {mathcal {F}}-SU(5) in the right direction

The Fermi National Accelerator Laboratory (FNAL) recently announced confirmation of the Brookhaven National Lab (BNL) measurements of the g-2 of the muon that uncovered a discrepancy with the theoretically calculated Standard Model value. We suggest an explanation for the combined BNL+FNAL 4.2sigma deviation within the supersymmetric grand unification theory (GUT) model No-Scale {mathcal {F}}-SU(5) supplemented with a string derived TeV-scale extra 10+overline{10} vector-like multiplet and charged vector-like singlet (XE,XE^c), dubbed flippons. We introduced these vector-like particles into No-Scale Flipped SU(5) many years ago, and as a result, the renormalization group equation (RGE) running was immediately shaped to produce a distinctive and rather beneficial two-stage gauge coupling unification process to avoid the Landau pole and lift unification to the string scale, in addition to contributing through 1-loop to the light Higgs boson mass. The flippons have long stood ready to tackle another challenge, and now do so yet again, where the charged vector-like “lepton”/singlet couples with the muon, the supersymmetric down-type Higgs H_d, and a singlet S, using a chirality flip to easily accommodate the muonic g-2 discrepancy in No-Scale {mathcal {F}}-SU(5). Considering the phenomenological success of this string derived model over the prior 11 years that remains accommodative of all presently available LHC limits plus all other experimental constraints, including no fine-tuning, and the fact that for the first time a Starobinsky-like inflationary model consistent with all cosmological data was derived from superstring theory in No-Scale Flipped SU(5), we believe it is imperative to reconcile the BNL+FNAL developments within the model space.

Resolving the (g \u2212 2)\u03bc discrepancy with mathcal{F} \u2013SU(5) intersecting D-branes

A discrepancy between the measured anomalous magnetic moment of the muon (g − 2)μ and computed Standard Model value now stands at a combined 4.2σ following experiments at Brookhaven National Lab (BNL) and the Fermi National Accelerator Laboratory (FNAL). A solution to the disagreement is uncovered in flipped SU(5) with additional TeV-Scale vector-like 10 + overline{mathbf{10}} multiplets and charged singlet derived from local F-Theory, collectively referred to as mathcal{F} –SU(5). Here we engage general No-Scale supersymmetry (SUSY) breaking in mathcal{F} –SU(5) D-brane model building to alleviate the (g −2)μ tension between the Standard Model and observations. A robust ∆aμ(SUSY) is realized via mixing of M5 and M1X at the secondary SU(5) × U(1)X unification scale in mathcal{F} –SU(5) emanating from SU(5) breaking and U(1)X flux effects. Calculations unveil ∆aμ(SUSY) = 19.0–22.3 × 10−10 for gluino masses of M( overset{sim }{g} )= 2.25–2.56 TeV and higgsino dark matter, aptly residing within the BNL+FNAL 1σ mean. This (g − 2)μ favorable region of the model space also generates the correct light Higgs boson mass and branching ratios of companion rare decay processes, and is further consistent with all LHC Run 2 constraints. Finally, we also examine the heavy SUSY Higgs boson in light of recent LHC searches for an extended Higgs sector.

Muon (g \u2212 2) in the B-LSSM

The difference between the updated experimental result on the muon anomalous magnetic dipole moment and the corresponding theoretical prediction of the standard model on that is about 4.2 standard deviations. In this work, we calculate the muon anomalous MDM at the two-loop level in the supersymmetric B − L extension of the standard model. Considering the experimental constraints on the lightest Higgs boson mass, Higgs boson decay modes h → γγ, WW, ZZ, boverline{b} , tau overline{tau} , B rare decay overline{B} → Xsγ, and the transition magnetic moments of Majorana neutrinos, we analyze the theoretical predictions of the muon anomalous magnetic dipole moment in the B − L supersymmetric model. The numerical analyses indicate that the tension between the experimental measurement and the standard model prediction is remedied in the B − L supersymmetric model.

The light MSSM Higgs boson mass for large tan beta and complex input parameters

We discuss various improvements of the prediction for the light MSSM Higgs boson mass in the hybrid framework of the public code texttt {FeynHiggs}, which combines fixed-order and effective field theory results. First, we discuss the resummation of logarithmic contributions proportional to the bottom-Yukawa coupling including two-loop Delta _b resummation. For large tan beta , these improvements can lead to large upward shifts of the Higgs mass compared to the existing fixed-order calculations. Second, we improve the implemented EFT calculation by fully taking into account the effect of mathcal{CP}-violating phases. As a third improvement, we discuss the inclusion of partial hbox {N}^3LL resummation. The presented improvements will be implemented into texttt {FeynHiggs}.

Theoretical uncertainties in the MSSM Higgs boson mass calculation

The remaining theoretical uncertainties from unknown higher-order corrections in the prediction for the light Higgs-boson mass of the MSSM are estimated. The uncertainties associated with three different approaches that are implemented in the publicly available code FeynHiggs are compared: the fixed-order diagrammatic approach, suitable for low SUSY scales, the effective field theory (EFT) approach, suitable for high SUSY scales, and the hybrid approach which combines the fixed-order and the EFT approaches. It is demonstrated for a simple single-scale scenario that the result based on the hybrid approach yields a precise prediction for low, intermediate and high SUSY scales with a theoretical uncertainty of up to sim 1.5,, mathrm {GeV} for large stop mixing and sim 0.5,, mathrm {GeV} for small stop mixing. The uncertainty estimate of the hybrid calculation approaches the uncertainty estimate of the fixed-order result for low SUSY scales and the uncertainty estimate of the EFT approach for high SUSY scales, while for intermediate scales it is reduced compared to both of the individual results. The estimate of the theoretical uncertainty is also investigated in scenarios with more than one mass scale. A significantly enhanced uncertainty is found in scenarios where the gluino is substantially heavier than the scalar top quarks. The uncertainty estimate presented in this paper will be part of the public code FeynHiggs.

Updates and New Results in Models with Reduced Couplings

AbstractThe idea of reduction of couplings consists in searching for renormalization group invariant relations between parameters of a renormalizable theory that hold to all orders of perturbation theory. Based on the principle of the reduction of couplings, one can construct Finite Unified Theories which are supersymmetric Grand Unified Theories that can be made all‐order finite. The prediction of the top quark mass well in advance of its discovery and the prediction of the light Higgs boson mass in the range GeV much earlier than its discovery are among the celebrated successes of such models. Here, after a brief review of the reduction of couplings method and the properties of the resulting finiteness in supersymmetric theories, we analyse four phenomenologically favoured models: a minimal version of the , a finite , a finite model and a reduced version of the Minimal Supersymmetric Standard Model. A relevant update in the phenomenological evaluation has been the improved light Higgs‐boson mass prediction as provided by the latest version of FeynHiggs. All four models predict relatively heavy supersymmetric spectra that start just below or above the TeV scale, consistent with the non‐observation LHC results. Depending on the model, the lighter regions of the spectra could be accessible at CLIC, while the FCC‐hh will be able to test large parts of the predicted spectrum of each model. The lightest supersymmetric particle, a neutralino, is considered as a cold dark matter candidate and put to test using the latest MicrOMEGAs code.

The heavy gluino in natural no-scale [formula omitted]-SU(5)

In light of recent 80–137 fb−1 results at the LHC Run 2 establishing a lower gluino mass limit of 2.25 TeV, we revisit the supersymmetric GUT model Flipped SU(5) with extra vector-like particles, known as F-SU(5), with vanishing No-Scale Supergravity boundary conditions at the string scale of about 2×1017 GeV, including the supersymmetry breaking Bμ parameter which is strictly enforced as Bμ=0. Given the proportional dependence of all model scales on a single parameter M1/2, No-Scale F-SU(5) was shown to possess no electroweak fine-tuning and thus persists as a natural one-parameter model. In this fresh analysis here, we demand consistency with the measured 125 GeV light Higgs boson mass, though we forgo an upper limit on the lightest neutralino relic density. The resulting phenomenology delivers a gluino mass of M(g˜)≲7.5 TeV and a lightest supersymmetric particle (LSP) of M(χ˜10)≲1.6 TeV. In order to dilute the relic density down to the WMAP and Planck measurements, we rely upon a single cosmological master coupling λ6.

Phenomenology of Higgs bosons in inverse seesaw model with Type-X two Higgs doublet at the LHC

Type-X two Higgs doublet model is known to explain the muon g − 2 anomaly with a relatively light charged Higgs boson at large tan β. The light charged Higgs boson has been searched in the main τ ν mode at the colliders. Invoking a scenario of inverse seesaw as the origin of neutrino masses and mixing, the charged Higgs boson can decay additionally to right-handed neutrinos which leads to interesting phenomenology. Considering generic lepton flavour violating signatures at the final states, a 5σ discovery can be achieved with the early data of LHC, at 14 TeV, for relatively large inverse seesaw Yukawa coupling YN. The very light pseudoscalar and charged Higgs boson mass reconstruction are performed using the new modes and the results look promising. The inverse seesaw Yukawa coupling is shown to be probed down to YN ∼ 0.2 at HL LHC with 3000 fb−1.

Naturalness in D-brane inspired models

We examine the naturalness of the D-brane inspired model constructed in flipped SU(5) supplemented with vector-like particles at the TeV scale, dubbed flippons. We find the model can produce a mainly Higgsino-like lightest supersymmetric particle (LSP) and small light stops, as favored by naturalness. In fact, a large trilinear scalar At term at the electroweak (EW) scale creates a large mass splitting between the top squarks, driving the light stop to near degeneracy with an LSP that is almost all Higgsino, with Delta Mleft({tilde{t}}_1,{tilde{chi}}_1^0right) < 5GeV, evading the LHC constraint on {tilde{t}}_1to c{tilde{chi}}_1^0 thus far. Given the smallness of the light stop, generating a 125 GeV light Higgs boson mass is aided by one-loop contributions from the Yukawa couplings between the flippons and Higgs fields. The resulting parameter space satisfying naturalness is rather constrained, thus we assess its viability by means of comparison to the LHC constraint on soft charm jets and direction detection limits on spin-independent cross-sections. Finally, we compute the level of electroweak fine-tuning and uncover a region with ΔEW< 30, i.e., fine-tuning better than 3%, regarded as low electroweak fine-tuning. Given the small light stop, the electroweak fine-tuning from only the top squarks is of mathcal{O} (1), indicating no fine-tuning from neither the light stop {tilde{t}}_1 nor the heavy stop {tilde{t}}_2 .

MSSM Higgs benchmark scenarios for Run 2 and beyond: the low tan beta region

We propose two new benchmark scenarios for Higgs-boson searches in the Minimal Supersymmetric Standard Model (MSSM ). These scenarios are specifically designed for the low tan beta region. A light Higgs-boson mass prediction compatible with the observed value of 125,hbox {GeV} is ensured in almost the entire parameter space by employing a flexible supersymmetric (SUSY) mass scale, reaching values of up to 10^{16},hbox {GeV}. The MSSM Higgs-sector predictions are evaluated in an effective field theory (EFT ) framework that exhibits a Two-Higgs-Doublet-Model at the low scale. In the first scenario all SUSY particles are relatively heavy, whereas the second scenario features light neutralinos and charginos. Both scenarios are largely compatible with the most recent results from Run 2 of the LHC , and we highlight the main phenomenological features relevant for future LHC searches. In particular, we provide a detailed discussion of heavy Higgs-boson decays to neutralinos and charginos in the second scenario, and the arising collider signatures, in order to facilitate the design of dedicated LHC searches in the near future.

Inspiration from intersecting D-branes: general supersymmetry breaking soft terms in no-scale mathcal{F}-SU(5)

Motivated by D-brane model building, we evaluate the mathcal {F}-SU(5) model with additional vector-like particle multiplets, referred to as flippons, within the framework of No-Scale Supergravity with non-vanishing general supersymmetry breaking soft terms at the string scale. The viable phenomenology is uncovered by applying all current experimental constraints, including but not limited to the correct light Higgs boson mass, WMAP and Planck relic density measurements, and several LHC constraints on supersymmetric particle spectra. Four interesting regions of the parameter space arise, as well as mixed scenarios, given by: (1) light stop coannihilation; (2) pure Higgsino dark matter; (3) Higgs funnel; and (4) light stau coannihilation. All regions can generate the observed value of the relic density commensurate with a 125 GeV light Higgs boson mass, with the exception of the relatively small relic density value for the pure Higgsino lightest supersymmetric particle. This work is concluded by gauging the model against present LHC search constraints and derivation of the final states observable at the LHC for each of these scenarios.

Complete two-loop QCD contributions to the lightest Higgs-boson mass in the MSSM with complex parameters

Higher-order corrections to the MSSM Higgs-boson masses are desirable for accurate predictions currently testable at the LHC. By comparing the prediction with the measured value of the discovered Higgs signal, viable parameter regions can be inferred. For an improved theory accuracy, we compute all two-loop corrections involving the strong coupling for the Higgs-boson mass spectrum of the MSSM with complex parameters. Apart from the dependence on the strong coupling, these contributions depend on the weak coupling and Yukawa couplings, leading to terms of mathcal {O}{left( alpha alpha _sright) } and mathcal {O}{left( sqrt{alpha _{q_1}}sqrt{alpha _{q_2}}alpha _sright) }, (q_{1,2}=t,b,c,s,u,d). The full dependence on the external momentum and all relevant mass scales is taken into account. The calculation is performed in the Feynman-diagrammatic approach which is flexible in the choice of the employed renormalization scheme. For the phenomenological results presented here, a renormalization scheme consistent with higher-order corrections included in the code FeynHiggs is adopted. For the evaluation of the results, a total of 513 two-loop two-point integrals with up to five different mass scales are computed fully numerically using the program SecDec. A comparison with existing results in the limit of real parameters and/or vanishing external momentum is carried out, and the impact on the lightest Higgs-boson mass is discussed, including the dependence on complex phases. The new results will be included in the public code FeynHiggs.

Probing the No-Scale [formula omitted]-SU(5) one-parameter model via gluino searches at the LHC2

In our recent paper entitled “The return of the King: No-Scale F-SU(5)”, we showed that the model space supporting the most favorable phenomenology should have been probed in 2016 at the LHC2, with an even further reach into this region of the model in 2017–18. This ideal realm of the one-parameter version of No-Scale F-SU(5) yields a 1.9–2.3 TeV gluino mass at the very same point where the light Higgs boson mass enters its rather narrow experimentally determined range of mh=125.09±0.24 GeV. Given the recent results reported at Moriond 2017 for 36 fb−1 of luminosity collected in 2016 at the 13 TeV LHC2, we now update the status of the No-Scale F-SU(5) model space in light of the gluino mass exclusion limits presented by the ATLAS and CMS Collaborations. We illustrate that a resolution could be reached soon as to whether supersymmetry lives in this most critical region of the model space.

Dark matter in split SUSY with intermediate higgses

The searches for heavy Higgs bosons and supersymmetric (SUSY) particles at the LHC have left the minimal supersymmetric standard model (MSSM) with an unusual spectrum of SUSY particles, namely, all squarks are beyond a few TeV while the Higgs bosons other than the one observed at 125 GeV could be relatively light. In light of this, we study a scenario characterized by two scales: the SUSY breaking scale or the squark-mass scale $(M_S)$ and the heavy Higgs-boson mass scale $(M_A)$.We perform a survey of the MSSM parameter space with $M_S < 10^{10}$ GeV and $M_A < 10^4$ GeV such that the lightest Higgs boson mass is within the range of the observed Higgs boson as well as satisfying a number of constraints. The set of constraints include the invisible decay width of the $Z$ boson and that of the Higgs boson, the chargino-mass limit, dark matter relic abundance from Planck, the spin-independent cross section of direct detection by LUX, and gamma-ray flux from dwarf spheroidal galaxies and gamma-ray line constraints measured by Fermi LAT. Survived regions of parameter space feature the dark matter with correct relic abundance, which is achieved through either coannihilation with charginos, $A/H$ funnels, or both. We show that future measurements, e.g., XENON1T and LZ, of spin-independent cross sections can further squeeze the parameter space.

Rare top-quark decays to Higgs boson in MSSM

In full one-loop generality and in next-to-leading order in QCD, we study rare top to Higgs boson flavour changing decay processes $t\to q h$ with $q=u,c$ quarks, in the general MSSM with R-parity conservation. Our primary goal is to search for enhanced effects on $Br(t\to q h)$ that could be visible at current and high luminosity LHC running. To this end, we perform an analytical expansion of the amplitude in terms of flavour changing squark mass insertions that treats both cases of hierarchical and degenerate squark masses in a unified way. We identify two enhanced effects allowed by various constraints: one from holomorphic trilinear soft SUSY breaking terms and/or right handed up squark mass insertions and another from non-holomorphic trilinear soft SUSY breaking terms and light Higgs boson masses. Interestingly, even with $\mathcal{O}(1)$ flavour violating effects in the, presently unconstrained, up-squark sector, SUSY effects on $Br(t\to q h)$ come out to be unobservable at LHC mainly due to leading order cancellations between penguin and self energy diagrams and the constraints from charge- and colour-breaking minima (CCB) of the MSSM vacuum. An exception to this conclusion may be effects arising from non-holomorphic soft SUSY breaking terms in the region where the CP-odd Higgs mass is smaller than the top-quark mass but this scenario is disfavoured by recent LHC searches. Our calculations for $t\to q h$ decay are made available in SUSY_FLAVOR numerical library.

One-parameter model for the superworld

We review the No-Scale ℱ-SU(5) model with extra TeV-scale vector-like flippon multiplets and its associated collider phenomenology in the search for supersymmetry at the LHC. The model framework possesses the rather unique capacity to provide a light CP-even Higgs boson mass in the favored 124–126 GeV window while simultaneously retaining a testably light SUSY spectrum that is consistent with emerging low-statistics excesses beyond the Standard Model expectation in the ATLAS and CMS multijet data.

Momentum-dependent two-loop QCD corrections to the neutral Higgs-boson masses in the MSSM

Results are presented for the momentum dependent two-loop contributions of O(alpha_t alpha_s) to the masses and mixing effects in the Higgs sector of the MSSM. They are obtained in the Feynman-diagrammatic approach using a mixed on-shell/DRbar renormalization that can directly be matched onto the higher-order corrections included in the code FeynHiggs. The new two-loop diagrams are evaluated with the program SecDec. The combination of the new momentum dependent two-loop contribution with the existing one- and two-loop corrections in the on-shell/DRbar scheme leads to an improved prediction of the light MSSM Higgs boson mass and a correspondingly reduced theoretical uncertainty. We find that the corresponding shifts in the lightest Higgs-boson mass M_h are below 1 GeV in all scenarios considered, but can extend up to the level of the current experimental uncertainty. The results are included in the code FeynHiggs.